"Unsupported system type" in hydra, reproduces fine locally

Development Hydra
1

hiya! while getting ready to upgrade to 26.05, I’ve noticed that one of my hosts has consistently stopped evaluating in Hydra with the error Unsupported system type

Now from what I understand this is usually for i.e doing x86_64-linux to aarch64-linux on a builder that doesn’t have that configured, though this is x86_64-linux all the way through so that’s it.

next I thought to run the Reproduce locally nix build command that hydra gives on the same builder and as the hydra user, and it seems to evaluate and build fine that way. Force-rebuilding yields nothing, and Hydra’s logs haven’t been too useful either.

Some extra context:

hydra configuration: tasiaiso/nixos-config: hydra.nix

the build that is failing: Hydra - Build 2891 of job tasiaiso:nixos-config-dev:hosts.qwertz

Another relevant piece of info might be that we’re running lix, but I’m not sure.

nix –version output:

nix (Lix, like Nix) 2.93.4 
System type: x86_64-linux 
Additional system types: aarch64-linux, i686-linux 
Features: gc, signed-caches 
System configuration file: /etc/nix/nix.conf 
User configuration files: /var/lib/hydra/.config/nix/nix.conf:/etc/xdg/nix/nix.conf:/var/lib/hydra/.nix-profile/etc/xdg/nix/nix.conf:/nix/profile/etc/xdg/nix/nix.conf:/var/lib/hydra/.local/state/nix/profile/
etc/xdg/nix/nix.conf:/etc/profiles/per-user/hydra/etc/xdg/nix/nix.conf:/nix/var/nix/profiles/default/etc/xdg/nix/nix.conf:/run/current-system/sw/etc/xdg/nix/nix.conf 
Store directory: /nix/store 
State directory: /nix/var/nix 
Data directory: /nix/store/04fzclc8sa1ziv056i3ljnj9qy5kabay-lix-2.93.4/share
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small update: I changed absolutely fuckall and it just fixed itself. fml we’ll never know how this piece of software works :sob:

the only thing I can recommend when this happens is getting the build command from Reproduce locally and running it as the hydra user. I assume that it copied the working derivation into the store which is why hydra could then skip it. If it wasn’t that then IDFK what it was.

An easy way to do this is like this (assuming you have sudo): sudo -u hydra -- nix build ...

alternatively, with doas: doas -u hydra nix build... (IIRC? doing this off of memory…)

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